I’ve recently started using NTRIP for RTK corrections to extend my working range, and it’s been working really well.
One challenge I can still run into is the lack of local benchmarks in some areas of work in, which led me down the rabbit hole of CORS systems. I was about to sign up for a paid subscription service when I discovered that AUSCORS (through AUSPOS) can be used over NTRIP for free
I’ve connected to a local AUSCORS tower and am getting a fix, but I haven’t run any accuracy tests yet. That said, my biggest question is… why is it free? Seriously, why are private CORS services charging $3,000 per year while AUSCORS is available at no cost?
I’m still learning, but if I’m within 30 km of a CORS station, I should be getting 2–3 cm accuracy, which is perfectly fine for my work. So, what’s the real advantage of paid services like HEX or SmartNet? Are they more reliable, or is there something I’m missing?
The CORS Stations that are managed by GA are provided for free, yes; but their accuracy/reliability is no different to that of the Paid providers.
Smartnet, AllDayRTK, etc. include these bases in their own offerings, but Smartnet, AllDayRTK, etc. also manage some of their own CORS Stations in different locations across Australia (and the world) that don’t go through GA’s network. Some providers also provide VRS options, but they all (should) share the same requirement for a Regulation 13 Certificate to operate as a CORS in Australia and provide positional accuracy in Law.
If you aren’t after absolute accuracy at 30km, using GA’s offering is okay. If you are wanting better accuracy, you are going to want to either look at the other providers who have a base closer to your work location, or maybe use that annual fee towards running your own base.
Thanks Joel, I’ll look into the others too see if there map represents a better solution for my work areas to see if it’s worth the cost.
I was able to run a test today using the AUSPOS over Ntrip and staked out some local State benchmarks, very interesting to see that the eastings are spot on but all northings where about 6cm off? I’m 20km from the base almost directly south from it not far off to the east. Coincidence or is this how the error works with base station distance?
My plan is to in remote areas where cell reception is bad is to connect to the AUSPOS and establish a single point on site and then set my base station on top of it and switch back to tradition base and rover over Lora. AUSPOS Test copy.pdf (65.3 KB)
I am not familiar with the Victorian system, but I can see on the mark report (from their control database) a few things.
1 - It was established on a cadastral survey. This likely means the co-ordinates are derived or scaled from plans.
2 - The co-ordinates (on 1994 datum) are only to two decimal places.
3 - When then transformed to GDA2020, the numbers are only as good as what has been fed in.
I would see if you can find another mark which is published as a GDA Datum (Like 342100691, which has an uncertainty published of 0.025) to perhaps compare against?
Joel is on the ball here; you could also try 342100191 with an uncertainty 0.017 and it’s usually accessible and open (used to live there) but there may be some building works.
And bear in mind it’s a closed loop, GA who provide you the AUSPOS position and NTRIP also calibrate and issue the Reg 13’s so they should be (all other things being equal) very close at the few mm level.
FYI Reg 13 is more accurate as it uses a full 7 day observation and utilizes the whole APREF network of ~ 970 stations compared to an AUSPOS position which uses 15 stations and whatever time you manage to put in, but normally needs 8 hours+ to reach cm level
Which leads to the obvious question for your RTK, how long you are averaging those positions you are collecting? If you want to split hairs, I would be giving them as long as possible say at least 2 or 3 mins.
I also gather you are using GLNG for your NTRIP, if so switch to WPND. I was involved with is recalibration a couple years ago and it’s now a goodie and will nearly halve your baseline so a much better source for you there.
Remember at 1ppm every extra 10km is another 1cm uncertainty.
Here in the USA SC, I often check the state’s RTN against passive control marks with my Emlids and Javad’s. I’m always within 1-2cm in both components.
